Generally tire wear causes significant changes in tire performance, a drop in draining performance on wet road surfaces being among them, depending of the degree of wear. Therefore, it is important to detect the condition of tires coming in contact with the road surface, especially, the degree of wear, if the safety of vehicular operation is to be enhanced. If tire wear further advances, there will be greater risks of tire burst.
A method for estimating the amount of tire wear, as shown in FIGS. 8A to 8C, proposes the use of a tire-mounted unit 50 comprising a resistance means 51, which has a plurality of resistors 51a, each being a conductive rubber member, and a resistive element 51b connected in parallel with the resistors 51a, a sensor 53, which is provided with a DC power supply 52 connected in series with the resistance means 51, and a transmitter 55, which transmits detection signals of the sensor 53 through an antenna 54. The tire-mounted unit 50 is embedded in a block 61 of a tire tread 60, and the amount of wear of the tire tread 60 is estimated by detecting the resistance value of the resistance means 51 which changes with the wear of the block 60. (Refer to Patent Document 1, for example).    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2005-28950